Fully open the dampers underneath the charcoal grill and on the lid of the grill.
Light the fire and leave the dampers wide open as the charcoal begins to burn. Keeping the dampers open will allow as much oxygen as possible to enter the grill and stoke the fire. The cover should remain off while lighting.
Adjust the dampers underneath the grill for your desired cooking level. Leave the dampers wide open for the hottest fire. This would be suitable for something like steaks. Close the dampers 1/4 of the way to lower the heat for indirect cooking. Chicken is a common food prepared with indirect heating method. For even lower temperatures, close the dampers halfway or even 3/4. Never close them fully or you will risk putting out the charcoal.
Use the dampers on the grill's lid to further control the heat. Closed dampers will create a cooler fire, while wide open dampers will create the hottest fire. Experiment with the dampers on the lid to accommodate your food.